Effect of ceftiofur on mesophilic anaerobic digestion of dairy manure and the reduction of the cephalosporin-resistance gene cmy-2

Abstract

The effect of ceftiofur (CEF), a commonly used antibiotics on dairy farms, on the performance and stability of mesophilic batch anaerobic digestion (AD) of dairy manure was evaluated in terms of methane production, organic matter removal (COD, dCOD, TS, and VS), and synthesis of end-products (VFAs, CO2, and H2). The results indicated that only CEF concentrations of 10 mg/L or higher significantly affected the performance of the AD process, although the overall stability was not compromised. Biochemical analyses suggested that hydrolytic microorganisms were the most affected by the presence of CEF leading to lower COD removal, whereas acetogens were only temporarily slowed down. Methanogens, on the other hand, were not directly affected by any of the CEF concentrations tested (0.2–250 mg/L). Additionally, the presence of CEF was shown to alter the incidence of the cephalosporin-resistance marker, cmy-2, although an overall reduction was achieved in 15-day batch anaerobic digestion trials.